Traction nozzles are used in sewer pipe lines and other piping systems to assist in pulling high pressure hose into the pipe to reach obstructions requiring removal. These traction nozzles have jet tips oriented at an angle rearward in order to generate thrust in the nozzle within the pipe to assist in puffing the hose through and along long stretches of pipe and around pipe bends. These nozzles have forward directed jet tips and may also have laterally directed tips to ablate the obstructions encountered. However, the forward directed jet tips produce a counter force against forward travel of the nozzle through the pipe. This counterforce hinders effective deployment of the high pressure hose and reduces the net pulling force produced by the traction nozzle on the high pressure hose. Thus there is a need for a switching mechanism that does not generate a counterforce during traction operation, yet facilitates operation of an effective fluid jet nozzle during actual cleaning operations. Furthermore, there is a need for a nozzle assembly incorporating a switching valve assembly that is replaceable and has a minimum number of component parts in order to simplify design and maintenance of such a nozzle assembly.